1. Field of the Invention
The present invention relates to an apparatus for detecting abnormality of a vehicle sensor and a method, and particularly to an apparatus for detecting abnormality of a vehicle sensor and a method that detects for presence or absence of an abnormality of a sensor mounted to a vehicle.
2. Description of the Related Art
In order to restrain cross-slipping of a vehicle that is caused when a driver carries out an abrupt steering wheel operation for avoiding an obstacle or when a vehicle reaches a curve of a slippery road, a VSC (Vehicle Stability Control) system is known as a technology for ensuring stability of the vehicle by automatically controlling engine output and brake force at respective wheels. With this system, the stability of the vehicle is achieved by controlling the engine output and the brake force at the respective wheels by detecting cross-slipping of the vehicle with various sensors such as a yaw rate sensor, a steering angle sensor and a cross acceleration sensor. Therefore, when abnormalities are caused in the various sensors, detection accuracy of cross-slipping of the vehicle deteriorates and the vehicle may not be stabilized sufficiently.
Hence, it is necessary to detect presence or absence of abnormalities of the various sensors and, as a technology applicable thereto, there is provided a technology described in Japanese Patent Laid-Open No. 6-206569.
According to this technology, by calculating an estimated yaw rate on the basis of speeds of left and right wheels and comparing a result of this calculation with an output value of a yaw rate sensor, an abnormality of the yaw rate sensor can be detected. In this way, according to the technology described in Japanese Patent Laid-Open No. 6-206569, abnormality of the sensor is detected by comparing the sensor output with a value calculated (estimated) from a vehicle state utilizing steady state equations.
However, with the technology described in Japanese Patent Laid-Open No. 6-206569, when the vehicle does not grip the road, the steady state equations used in the calculation are not established and, therefore, there is a problem in that abnormalities of sensors may be detected erroneously.
The present invention has been created in order to resolve the above-described problem and an object of the present invention is to provide an apparatus for detecting abnormality of a vehicle sensor which apparatus is capable of preventing erroneous detection of abnormalities of sensors, and a method.
In order to achieve the above-described object, in a first aspect of the present invention, there is provided an apparatus for detecting abnormality of a vehicle sensor comprising: a first sensor for detecting an operational state of a vehicle; a second sensor, which is different from the first sensor, for detecting the operational state of the vehicle; an abnormality detecting device for detecting for presence of an abnormality of the first sensor on the basis of a predefined operational state of the vehicle detected by the first sensor and the predefined operational state of the vehicle estimated on the basis of an output of the second sensor; a grip degree detecting device for detecting grip degree of a wheel of the vehicle with respect to a road surface; and a prohibiting device for prohibiting detection for presence of an abnormality of the first sensor by the abnormality detecting device in at least one case of a case in which the grip degree is lower than a predetermined degree and a case in which a cross-gradient of the road surface is equal to or more than a predetermined value.
According to the apparatus of detecting abnormality of vehicular sensor of the present invention, presence or absence of an abnormality of the first sensor is detected by the abnormality detecting device on the basis of a predefined movement state of the vehicle detected by the first sensor, which is for detecting the operational state of the vehicle, and a predefined movement state of the vehicle estimated on the basis of the output of the second sensor, which is different from the first sensor.
Further, detection of presence or absence of an abnormality of the first sensor can be carried out by the abnormality detecting device, by assuming that the first sensor is abnormal when a difference between the predefined operational state of the vehicle detected by the first sensor and the predefined operational state of the vehicle estimated on the basis of the output of the second sensor is larger than a previously determined threshold value, assuming that the first sensor is abnormal when a ratio of the predefined operational state of the vehicle detected by the first sensor to the predefined operational state of the vehicle estimated on the basis of output of the second sensor is larger than a previously determined ratio, or the like.
Moreover, all sensors mounted to the vehicle can be included in the first sensor and the second sensor of the present invention.
Furthermore, in the present invention, the grip degree of the wheel with respect to the road is detected by the grip degree detecting device, and detection of presence or absence of an abnormality of the first sensor by the abnormality detecting device is prohibited by the prohibiting device in at least one case of the case in which the grip degree is lower than the predetermined degree and the case in which the cross gradient of the road is equal to or larger than the predetermined value.
That is, in at least one of the case in which the grip degree of the wheel with respect to the road is low and the case in which the cross gradient of the road is large, steady state equations are not established, and the predefined operational state of the vehicle estimated on the basis of the second sensor has low reliability. Therefore, in this case, the detection of presence or absence of an abnormality is not carried out.
In this way, according to the apparatus for detecting abnormality of a vehicle sensor of the present invention, in at least one case of the case in which the grip degree of the wheel with respect to the road is lower than the predetermined degree and the case in which the cross gradient of the road is equal to or larger than the predetermined value, abnormality detection for sensors constituting an object of abnormality detection is prohibited. Thus, erroneous detection of abnormalities of sensors can be preemptively prevented.
In this case, the first sensor in the apparatus for detecting abnormality of a vehicle sensor according to the present invention can be at least one of a cross acceleration sensor, a yaw rate sensor and a steering angle sensor. As described above, according to a VSC system, cross-slipping of the vehicle is detected by the cross acceleration sensor, the yaw rate sensor and the steering angle sensor. Therefore, by having as the first sensor, which is the subject of abnormality detection in the present invention, at least one of the cross acceleration sensor, the yaw rate sensor and the steering angle sensor, control by the VSC system can be made highly accurate in the case of applying the present invention in the VSC system.
Further, a wheel speed sensor may be applied as the second sensor of the present invention.
Furthermore, in a second aspect of the present invention, there is provided an apparatus for detecting abnormality of a vehicle sensor according to the first aspect, wherein a yaw rate sensor and a cross-acceleration sensor serve as the first sensor, and the abnormality detecting device detects for presence of an abnormality of the yaw rate sensor on the basis of a yaw rate detected by the yaw rate sensor and a yaw rate estimated on the basis of the output of the second sensor; in a case where an abnormality of the yaw rate sensor is not detected, the cross-acceleration sensor serves as the first sensor, the yaw rate sensor serves as the second sensor, and the abnormality detecting device detects for presence of an abnormality of the cross-acceleration sensor on the basis of a cross-acceleration detected by the cross-acceleration sensor and a cross-acceleration estimated on the basis of an output of the yaw rate sensor; and in a case where an abnormality of the yaw rate sensor is detected, the cross-acceleration sensor serves as the first sensor, a sensor other than the yaw rate sensor serves as the second sensor, and the abnormality detecting device detects for presence of an abnormality of the cross-acceleration sensor on the basis of the cross-acceleration detected by the cross-acceleration sensor and a cross-acceleration estimated on the basis of an output of the sensor other than the yaw rate sensor.
In this case, when the yaw rate sensor is abnormal, the cross acceleration is estimated without using the output of the yaw rate sensor. Accordingly, erroneous detection of an abnormality of the cross acceleration sensor can be prevented.
Furthermore, in a third aspect of the present invention, there is provided an apparatus for detecting abnormality of a vehicle sensor according to the first aspect, wherein: a yaw rate sensor and a cross-acceleration sensor serve as the first sensor, a wheel speed sensor serves as the second sensor, the abnormality detecting device detects for presence of an abnormality of the yaw rate sensor on the basis of a yaw rate detected by the yaw rate sensor and a yaw rate estimated on the basis of an output of the wheel speed sensor; the abnormality detecting device detects for presence of an abnormality of the cross-acceleration sensor on the basis of a cross-acceleration detected by the cross-acceleration sensor and a cross-acceleration estimated on the basis of the output of the wheel speed sensor; in a case where the yaw rate sensor and the cross-acceleration sensor are normal, the abnormality detecting device detects for presence of an abnormality of the steering angle sensor on the basis of the yaw rate detected by the yaw rate sensor and a yaw rate estimated on the basis of the cross-acceleration detected by the cross-acceleration sensor, the output of the wheel speed sensor, and an output of the steering angle sensor.
Furthermore, in a fourth aspect of the present invention, there is provided an apparatus for detecting abnormality of a vehicle sensor according to the third aspect, wherein: in a case where the abnormality detecting device detects presence of an abnormality of the cross-acceleration sensor on the basis of the cross-acceleration detected by the cross-acceleration sensor and the cross-acceleration estimated on the basis of the output of the wheel speed sensor, on the basis of the cross-acceleration detected by the cross-acceleration sensor and a cross-acceleration estimated on the basis of an output of a predetermined measuring device, which of: an abnormality of the cross-acceleration sensor itself, or a cause other than the abnormality of the cross-acceleration sensor itself, is a cause of detection of the abnormality of the cross-acceleration sensor, is determined.
Furthermore, in a fifth aspect of the present invention, there is provided an apparatus for detecting abnormality of vehicle sensor according to the fourth aspect, wherein the predetermined measuring device is a slip angle measuring device for measuring a vehicle body slip angle, and the abnormality detecting device determines, on the basis of the cross-acceleration detected by the cross-acceleration sensor and a cross-acceleration estimated on the basis of an output of the slip angle measuring device, whether the detection of the abnormality of the cross-acceleration sensor is due to the abnormality of the cross-acceleration sensor itself, or the detection of the abnormality of the cross-acceleration sensor is rather than due to the abnormality of the cross-acceleration sensor itself, due to the cross-gradient being larger than a predetermined value.
Furthermore, in a sixth aspect of the present invention, there is provided an apparatus for detecting abnormality of vehicle sensor according to the first aspect, further comprising: a cross-gradient detecting device for detecting the cross-gradient of the road surface, wherein before the abnormality detecting device detecting for presence of an abnormality of the first sensor, the grip degree and the cross-gradient of the road surface is detected.
Furthermore, in a seventh aspect of the present invention, there is provided a method for detecting abnormality of a vehicle sensor comprising: detecting an operational state of a vehicle by a first sensor; detecting the operational state of the vehicle by a second sensor, which is different from the first sensor; detecting presence of an abnormality of the first sensor on the basis of a predefined operational state of the vehicle detected by the first sensor and the predefined operational state of the vehicle estimated on the basis of an output of the second sensor; detecting grip degree of a wheel of the vehicle with respect to a road surface; and prohibiting detection for presence of an abnormality of the first sensor in at least one case of a case in which the grip degree is lower than a predetermined degree and a case in which a cross-gradient of the road surface is equal to or more than a predetermined value.
Furthermore, in a eighth aspect of the present invention, there is provided an apparatus for detecting abnormality of a vehicle sensor comprising: a first sensor for detecting an operational state of a vehicle; a second sensor, which is different from the first sensor, for detecting the operational state of the vehicle; an abnormality detecting device for detecting for presence of an abnormality of the first sensor on the basis of a predefined operational state of the vehicle detected by the first sensor and the predefined operational state of the vehicle estimated on the basis of an output of the second sensor; a grip degree detecting device for detecting grip degree of a wheel of the vehicle with respect to a road surface; and a prohibiting device for prohibiting detection for presence of an abnormality of the first sensor by the abnormality detecting device in at least one case of a case in which the grip degree is lower than a predetermined degree and a case in which a cross-gradient of the road surface is equal to or more than a predetermined value, wherein the first sensor is at least one of a cross-acceleration sensor, a yaw rate sensor and a steering angle sensor, and the second sensor is a wheel speed sensor.
Furthermore, in a ninth aspect of the present invention, there is provided a method for detecting abnormality of a vehicle sensor comprising: detecting an operational state of a vehicle by a first sensor; detecting the operational state of the vehicle by a second sensor, which is different from the first sensor; detecting presence of an abnormality of the first sensor on the basis of a predefined operational state of the vehicle detected by the first sensor and the predefined operational state of the vehicle estimated on the basis of an output of the second sensor; detecting grip degree of a wheel of the vehicle with respect to a road surface; and prohibiting detection for presence of an abnormality of the first sensor in at least one case of a case in which the grip degree is lower than a predetermined degree and a case in which a cross-gradient of the road surface is equal to or more than a predetermined value.
Furthermore, in a tenth aspect of the present invention, there is provided an apparatus for detecting abnormality of a vehicle sensor comprising: a first sensor for detecting an operational state of a vehicle; a second sensor, which is different from the first sensor, for detecting the operational state of the vehicle; an abnormality detecting device for detecting for presence of an abnormality of the first sensor on the basis of a predefined operational state of the vehicle detected by the first sensor and the predefined operational state of the vehicle estimated on the basis of an output of the second sensor; a grip degree detecting device for detecting grip degree of a wheel of the vehicle with respect to a road surface; and a prohibiting device for prohibiting detection for presence of an abnormality of the first sensor by the abnormality detecting device in at least one case of a case in which the grip degree is lower than a predetermined degree and a case in which a cross-gradient of the road surface is equal to or more than a predetermined value, wherein the first sensor is at least one of a cross-acceleration sensor, a yaw rate sensor and a steering angle sensor, and the second sensor is a wheel speed sensor.